Hot carrier generation, optical chirality, and Raman enhancement in heterostructures

This study presents a detailed electromagnetic investigation of hot-carrier generation, local optical chirality, and Raman enhancement in bimetallic core-shell-satellite nanostructures. Four representative configurations: Au-Pd, Ag-Pd, Au@Ag-Pd, and Ag@Au-Pd, were modeled to explore how core-shell arrangements of Au and Ag, in combination with Pd nanoparticle, influence their optical responses. Real-space distributions of hot-carrier generation rates reveal that Au-based systems support broader and more intense plasmonic excitations, while Ag-based counterparts exhibit sharper, more confined hot-carrier localization. Calculations of the local density of optical chirality (LDOC) and the polarization-resolved optical-activity LDOC (OA-LDOC) show that the core-shell structure induces spatially asymmetric chiral fields, with the Ag@Au-Pd configuration demonstrating the highest sensitivity to polarization. Raman enhancement factors, derived from near-field intensity profiles, highlight the critical role of interfacial composition in modulating surface-enhanced Raman scattering (SERS) performance. Overall, these findings elucidate field-driven phenomena in complex plasmonic heterostructures and point to promising strategies for tailored applications in photocatalysis, chiral molecular sensing, and nonlinear optical systems.